Heretofore, it has been a conventional practice that when an abnormality or failure occurs at, for example, an engine in a vehicle such as an automobile, such an abnormality or failure is evaluated from an abnormal sound generated by the engine. Usually, a technician visits, for example, a car dealer or a service garage to which the vehicle has been brought and conduct such abnormality evaluation based on abnormal sound by listening to an abnormal sound at that site. In such a case, if the evaluation cannot reach a conclusion, documents concerning abnormal sounds that have been so far collected are searched for the description of an abnormal sound substantially the same as the abnormal sound under evaluation to judge whether the sound in question is abnormal. Alternatively, if the abnormality judgment is impossible at the site, the vehicle is carried to a garage that is capable of examining the vehicle or to the manufacturer of the vehicle and subjected to a noise and vibration evaluation (NV evaluation) for investigation of the cause by analysis. When the cause of the abnormal sound is found out then a proper measure is taken. Since such judgment based on human's sensitivity may vary with different evaluators, a system for evaluation based on fixed criteria has been desired.
On the other hand, one known technique for evaluating abnormality of a production line based on sound is a technique such that sound data obtained from a motor actuator for use in a vehicle air conditioner is analyzed using plural characteristic volumes to determine the condition of the motor actuator from the conclusion of the analysis, as described in Japanese Patent Laid-Open Gazette No. HEI 11-278041 for example. Another known technique described in Japanese Patent Laid-Open Gazette No. HEI 4-363641 is to compare an engine sound generated at starting to a reference engine sound and judge whether the battery or the starter as well as the alternator is in an abnormal condition on the basis of the result of the comparison.
The aforementioned abnormality evaluation device is adapted to judge whether abnormality occurs or not at the site where the sound is recorded. Such an adaptation is convenient if the abnormality judgment is made in a factory before shipment. However, if a vehicle already shipped has abnormality, the abnormality evaluation device has to be transported to a site where the vehicle to be evaluated for abnormality is located. For this reason, if the abnormality evaluation device is up-scaled to accommodate a large volume of data as criteria for judgment for a higher precision, the convenience in transporting such an up-scaled device is sometimes lowered.